Individual study: The effects of partial root pruning on new root formation of Nuttall oak Quercus nuttallii seedlings; a laboratory experiment, University of Memphis, Tennessee, USA
Farmer J.W. & Pezeshki S.R. (2004) Effects of periodic flooding and root pruning on Quercus nuttallii seedlings. Wetlands Ecology and Management, 12, 205-214
In the southern USA, much emphasis in bottomland hardwood restoration is placed on establishing an oak-dominated forest. Regeneration of deforested areas and where a desirable seed source is not present, by planting nursery-grown seedlings is one available reforestation technique. At the time of the present study, the usual procedure for seedling preparation was to prune seedling roots prior to transplanting in the field. However, it was not fully known as to what effect root pruning has on transplanted seedlings. Secondly, bottomland forest restoration efforts inherently take place on floodplains, but the potential interaction between root pruning and flooding on seedling performance was not known. This study consisted of two separate but related laboratory experiments. The second experiment, focusing on the effects of varying degrees of root pruning on new root formation, is summarised here.
For a summary of the effects of various amounts of root removal and varying soil moisture regimes on transplanted Nuttall oak Quercus nuttallii seedlings, see: http://www.conservationevidence.com/ViewEntry.asp?ID=1025.
One hundred and fifty bareroot Nuttall oak seedlings were obtained from a State nursery at Pinson, Tennessee; 45 of similar size (c. 25 cm tall, 5.2 mm basal diameter) were selected for root pruning. The experiment focused on the effects of varying degrees of root pruning on new root formation during the first 30 days.
Treatments: Treatments were 75% removal of each individual root's length, 25% removal, and a control (no root pruning), immediately after which seedlings were planted in 2.5 l plastic pots in a sand/field soil (1:2) mix. The seedlings were randomly arranged in the laboratory under artificial lighting. Samples were harvested at 0, 10, 20 and 30 days after treatment initiation, and analyzed for new root formation.
At day 10 there were no new root formations on any of the seedlings from the treatments. Root formation began sometime between day 10 and day 20. On day 20 there was considerable new root formation on both pruned and control seedlings.
Seedlings in the heavy pruned (75%) treatment produced an average of 13.0 new roots, 39.2 cm of new root length and 23.8 mg of new root biomass.
Seedlings in the light pruned (25%) treatment had an average of 8.6 new roots, 25.6 cm of new root length, and 17.0 mg of new root biomass.
Controls had an average of 5.6 new roots, 14.5 cm of new root length and 10.8 mg of new root biomass.
There was no difference in number of new roots, length of new root, or new root biomass at day 20 even though the heavy pruning had over twice as much root production as the control. Similar patterns were noted for day 30. New roots almost always emerged within 1 to 2 cm above the point at which the root was pruned.
Conclusions: Although some interesting trends were apparent e.g. the heavily pruned treatment resulted on average greatest new root production, the experiment did not reveal any significant differences in seedling root production between treatments in terms of new root formation, root length, or root biomass due to the pruning.
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